Predator shadows: complex life histories as generators of spatially patterned indirect interactions across ecosystems

Ecological coupling by material exchanges or dispersal between spatially distinct communities has important impacts on ecological processes, such as diversity–stability relationships, ecosystem function, and food web dynamics. One important mode of coupling between ecosystems occurs via organisms with complex life histories, which often switch between distinct ecosystems during their life cycle, and so can be channels of material exchanges between these ecosystems. Some organisms with complex life histories (e.g. frogs, dragonflies) can be abundant and effective predators during one or more life stages, and so provide conduits for strong direct and indirect interactions across ecosystem boundaries, linking the dynamics of discrete and often quite dissimilar community types. We present simple models and a case study (tailored to pond ecosystems), to explore how interactions within larval habitats can indirectly impact ecological interactions in adult habitats. Using our case study as a springboard, we propose that cohorts of predators emerging from natal habitats (e.g. ponds) cast 'predation shadows' on the surrounding adult (e.g. terrestrial) landscape. Trophic interactions within ponds, and the distribution of ponds on the landscape, can thus affect the spatial pattern in the strength of these predation shadows, creating strong spatial patterning in terrestrial trophic cascades. Our findings emphasize the importance of organisms with complex life histories as generators of strong links across ecosystem boundaries, and as potential sources of spatial variation in the strength and indirect impacts of interspecific interactions.     

Study of permeation and blocker binding in TMEM16A calcium-activated chloride channels

We studied the effects of mutations of positively charged amino acid residues in the pore of X. tropicalis TMEM16A calcium-activated chloride channels: K613E, K628E, K630E; R646E and R761E. The activation and deactivation kinetics were not affected, and only K613E showed a lower current density. K628E and R761E affect anion selectivity without affecting Na⁺ permeation, whereas K613E, R646E and the double mutant K613E + R646E affect anion selectivity and permeability to Na⁺. Furthermore, altered blockade by the chloride channel blockers anthracene-9-carboxylic acid (A-9-C), 4, 4''-Diisothiocyano-2,2''-stilbenedisulfonic acid (DIDS) and T16inh-A01 was observed. These results suggest the existence of 2 binding sites for anions within the pore at electrical distances of 0.3 and 0.5. These sites are also relevant for anion permeation and blockade.